[Mixed connective tissue disease with pulmonary hypertension developing in a chronic myeloid leukemia patient on dasatinib treatment].

A 37-year-old woman was diagnosed with chronic phase chronic myeloid leukemia. Nilotinib treatment was initiated; however, it had to be discontinued due to an allergic reaction one month later, and dasatinib treatment was provided. Although favorable response was obtained, she started complaining of shortness of breath 7 months after initiating dasatinib treatment. Chest X-ray and echocardiography indicated pulmonary congestion and hypertension. Further, she was diagnosed with mixed connective tissue disease (MCTD) based on Raynaud phenomenon, swollen fingers, sclerodactyly, pancytopenia, hypocomplementemia, and positive anti-U1-RNP antibody. Consequently, dasatinib treatment was discontinued, and she was administered prednisolone (1 mg/kg/day), which was effective and successfully tapered with concomitant administration of cyclophosphamide. This is the first case of MCTD that developed during dasatinib treatment. However, because the present case was a young woman, the development of MCTD could probably be attributed to autoimmune diatheses or it may be a coincidence. However, the possibility of patients receiving dasatinib treatment developing autoimmune diseases needs to be assessed.